1. Field of the Invention
The present invention relates to a disk device and, more particularly, to a disk device having improved cooling performance and dust purge performance of a driving unit of a head actuator using circulating air generated by the rotation of a magnetic disk, within a magnetic disk device.
2. Description of the Related Art
Conventionally, data of a computer is stored in a main memory of a storage device using a semiconductor element. Because information stored in the main memory disappears when power is not supplied, the data is also stored in an external storage device. In many cases, a magnetic disk device is used for this external storage device. Because of its large storage capacity, a hard disk device, including a data storage disk coated with a magnetic substance and a magnetic head for writing data onto and reading data from this disk, forms the external storage device. The data storage disk includes many disks of aluminum or glass coated with a magnetic substance and superimposed with each other. Data is written onto and read from this data storage disk, by rotating this disk by a motor.
The magnetic disk device has a spindle motor provided inside an enclosure. At least one magnetic disk is fitted to this spindle motor. The magnetic head provided on the head actuator is used to read recorded data from or write data onto the magnetic disk.
The head actuator swings around a rotation axis with a voice coil motor (VCM). The voice coil motor includes a magnet fitted to an upper yoke and a lower yoke, respectively, and a coil located in a magnetic field generated by the magnets. The head actuator swings around the rotation axis, based on a current conducted to the coil.
When the head actuator is made to swing around the rotation axis based on the current conducted to the coil, the coil is heated. Therefore, the coil needs to be cooled. According to a data storage device and a hard disk drive described in JP-A-11-110960, a slot or a groove is formed on a cavity wall of the disk device, or an isolation disk wall having an airflow channel formed therein is inserted (a shroud insert) to guide an airflow generated by the rotation of the disk through this airflow channel, thereby cooling the coil.
However, according to the configuration proposed by the data storage device and the hard disk drive described in JP-A-11-110960, the inflow amount of air is small, and the airflow cannot be efficiently applied to the end of the coil where the coil is heated most. Therefore, this method has a problem in that the effect of cooling the coil is small.
There is also a method of cooling a coil by guiding the airflow generated by the rotation of the disk to a coil part of a voice coil motor, using a shape of a magnetic circuit of the voice coil motor. However, according to this method, an airflow not contributing to the cooling is interrupted, and the amount of the airflow to a circulation filter provided in the downstream decreases. As a result, dust purge performance decreases.